More: Male teacher shortage affects boys who need role models
More: Career advice: How to become a substitute teacher
An unknown number of people who met state qualifications applied for the job, but were not hired, according to district officials.
The school now has a chemistry teacher, but the long-term vacancy raises questions about the freedom of principals to pick their team and whether they should fill the job immediately with the best person available or wait for someone who is a better fit for their team.
There are also possible legal implications because state law specifies a substitute teacher who is in a core class more than 20 days must be licensed and endorsed to teach that subject.
When asked about the credentials of the substitute in the BTW chemistry class, the district communications staff responded in an email: "All substitute teachers are required to have a bachelor's degree and a minimum GPA of 2.75."
Despite requests for clarification about whether the teacher had a teaching license and was endorsed to teach chemistry, the district did not provide additional information.
Tennessee Department of Education spokeswoman Sara Gast said the state will contact SCS "to learn more about this situation" and ensure systems are in place so it isn't repeated.
State records show the same chemistry teacher taught the class for the past three years, crediting that person with the test results of all the students from those years.
"If the chemistry teacher had left in November, this should not have been the case," Gast said.
District officials said the situation, where a long-term substitute was used for a vacant position for the better part of a year, was isolated to Booker T. Washington, and new practices are in place to prevent it from happening again.
"We know we did not do enough for our students," Chief of Communications Natalia Powers said.
Booker T. Washington in South Memphis was one of the first high schools in Memphis to serve African Americans. It now has about 600 students in grades 6 through 12.
President Obama gave the commencement speech at the school in 2011 after the students won a challenge "on the basis of its inspiring turn-around story," according to the White House at the time. In 2015-16, 86 percent of BTW students were considered economically disadvantaged, and more than one in five students had a disability.
Board chairwoman Shante Avant said the school's lack of a chemistry teacher for so long, even if the situation is now resolved, is of "deep concern" and "unacceptable."
"It's a hard pill for us to swallow to think our students didn't have what they needed at BTW," Avant said. "To the parents and those students, it's a heartfelt apology on my behalf that we didn't do what we needed to do."
After the 20th day of school into a new school year, SCS uses enrollment numbers to determine where more or fewer teachers or support staff are needed.
Last year, a school in the district's Innovation Zone turnaround program was in need of another teaching coach, Chief of Schools Sharon Griffin said. That job was posted; the chemistry teacher at Booker T. Washington applied and was hired and left immediately.
That left a vacancy at the school, which the principal filled with a substitute.
"At that time the principal and HR started collaborating, interviewing, advertising, going through the regular process," said Powers, the SCS communications chief. "Unfortunately, at the time we just didn't feel that the applicants met the expectations of the principal and the school."
The district did not respond to a question about how many qualified people applied.
"I don't think it's that they didn't meet the qualifications, I think it's just a matter of making sure the principal is satisfied with the candidates that he or she might be interviewing, that they have the right background," Powers said, noting that the school has recently seen several years of academic growth.
Booker T. Washington Principal Alisha Coleman-Kiner did not respond to requests for comment.
Board chairwoman Avant said autonomy for principals is beneficial, "but not without there being some standards that have to be met and supports for our kids."
Powers said the biology teacher at Booker T. Washington supported the substitute throughout the year, and the chemistry teacher who left also offered assistance in lesson planning.
Board member Chris Caldwell, whose district includes Booker T. Washington, said the test scores show the supports were "inadequate."
"It's very concerning to me, and we are not serving children well or in the way I hope we would when we allow this to happen," Caldwell said. "Certainly the kids deserve better."
To stay competitive in a county dense with school districts and other educational opportunities, Shelby County Schools must offer teachers an opportunity for advancement in their careers, Powers said.
But the district will take better care not to pull teachers away from their classrooms without a plan to fill that spot adequately, she said.
In the wake of questions from a reporter, Superintendent Dorsey Hopsey sent an email to school board members Friday saying that changes had been instituted because of the BTW matter.
"We flagged this situation last year and decided to closely monitor and restrict teacher promotions during the school year," Hopson said. "We certainly want our high performing employees to have an opportunity to move up in the District, but we also want to make sure we are making these decisions based on a timeline that best-serves our students."
Griffin said she's putting together a hiring timeline that would allow teachers to apply for open jobs, but would keep them in their current positions until the end of the school year or the start of the new fiscal year, which is July 1.
Chief of Human Resources Trinette Small said the district had "already made a decision in our budgeting cycle that where possible we would try to get positions posted earlier."
The hiring window can be narrow before the school year starts, Small said, as the budget isn't finalized until the end of June and the school year begins in early August.
The U.S. Department of Education's annual Teacher Shortage report identifies science teachers as difficult positions to fill in Tennessee dating back at least 20 years.
"Obviously there's a national teacher shortage and on a local level we are feeling the effects of it," Avant said.
Recent findings by the Economic Policy Institute, a D.C.-based think tank backed by labor unions, suggest that public schools are already in a teacher shortage bind: An Oct. 6 report found that given rising student populations, public schools are short by about 327,000 educators.
Two weeks before the beginning of this school year, district leaders said they were concerned about the 250 teaching positions still open across the district. That number is now down to 140 vacancies, according to Hopson's email, but 82 vacancies are new and are a result of increased enrollment.
The district is prioritizing vacancies pre-kindergarten and in classes that are required for graduation and have an end-of-class test, he said.
This year, SCS also employed a new strategy to fill open positions: the district hired a pool of licensed teachers to deploy to schools on the first day wherever there was an opening, avoiding the use of substitutes so early in the year.
Some of those people have since been hired into the roles they filled temporarily, Small said.
Avant said despite the new strategies and the known teacher shortage, she still wants additional answers about Booker T. Washington's chemistry classes last year.
"It isn't something that we want to have happen again," she said.
Contributing: Greg Toppo, USA TODAY. Follow Jennifer Pignolet on Twitter: @JenPignolet